The new Mazda6 offers only one engine, but the 2.5-liter SkyActiv four can be paired with either a six-speed automatic or a six-speed manual.

Toward the end of 2013, it will add a second offering: a 2.2-liter SkyActiv-D four-cylinder diesel engine, which competes directly with the VW Passat TDI--which is rated at a combined 35 mpg when fitted with a six-speed manual gearbox.

No word yet on any projected fuel-efficiency ratings for the diesel Mazda6, but that's one we'll be waiting eagerly to hear more about.